[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <253c6362834bf3c9deea94cfc7741920@suse.de>
Date: Sun, 16 Apr 2023 17:31:34 +0200
From: Oscar Salvador <osalvador@...e.de>
To: Mel Gorman <mgorman@...hsingularity.net>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Vlastimil Babka <vbabka@...e.cz>,
Michal Hocko <mhocko@...e.com>,
Oscar Salvador <OSalvador@...e.com>,
Yuanxi Liu <y.liu@...uida.com>,
David Hildenbrand <david@...hat.com>,
Matthew Wilcox <willy@...radead.org>,
Linux-MM <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: page_alloc: Skip regions with hugetlbfs pages when
allocating 1G pages
On 2023-04-14 16:14, Mel Gorman wrote:
> A bug was reported by Yuanxi Liu where allocating 1G pages at runtime
> is
> taking an excessive amount of time for large amounts of memory. Further
> testing allocating huge pages that the cost is linear i.e. if
> allocating
> 1G pages in batches of 10 then the time to allocate nr_hugepages from
> 10->20->30->etc increases linearly even though 10 pages are allocated
> at
> each step. Profiles indicated that much of the time is spent checking
> the
> validity within already existing huge pages and then attempting a
> migration
> that fails after isolating the range, draining pages and a whole lot of
> other useless work.
>
> Commit eb14d4eefdc4 ("mm,page_alloc: drop unnecessary checks from
> pfn_range_valid_contig") removed two checks, one which ignored huge
> pages
> for contiguous allocations as huge pages can sometimes migrate. While
> there may be value on migrating a 2M page to satisfy a 1G allocation,
> it's
> potentially expensive if the 1G allocation fails and it's pointless to
> try moving a 1G page for a new 1G allocation or scan the tail pages for
> valid PFNs.
>
> Reintroduce the PageHuge check and assume any contiguous region with
> hugetlbfs pages is unsuitable for a new 1G allocation.
>
> The hpagealloc test allocates huge pages in batches and reports the
> average latency per page over time. This test happens just after boot
> when
> fragmentation is not an issue. Units are in milliseconds.
>
...
>
> BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=217022
> Fixes: eb14d4eefdc4 ("mm,page_alloc: drop unnecessary checks from
> pfn_range_valid_contig")
> Reported-by: Yuanxi Liu <y.liu@...uida.com>
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
Reviewed-by: Oscar Salvador <osalvador@...e.de>
Thanks Mel!
--
Oscar Salvador
SUSE Labs
Powered by blists - more mailing lists